Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as mp3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise canceling using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
In many noise cancellation systems, it is desirable to include both feedforward noise cancellation by using a feedforward adaptive filter for generating a feedforward anti-noise signal from a reference microphone signal configured to measure ambient sounds and feedback noise cancellation by using a fixed-response feedback filter for generating a feedback noise cancellation signal to be combined with the feedforward anti-noise signal. However, using traditional approaches, when a gain of the feedback path is strong, the response of the feedforward adaptive filter may diverge, thus rendering the adaptive system unstable.